CT and high-resolution CT (HRCT) are both important modalities for imaging lung chronic disease, and certain features (distribution of disease in the axial plane, unilateral or bilateral disease, bronchovascular bundle thickening, septal thickening, central dot thickening, polygons, distortion of parenchyma, air-space disease, nodules) are well known to suggest specific diagnoses. In a series of 54 consecutive patients with six specific diseases (scleroderma or UIP, sarcoidosis, lymphangitic carcinomatosis, drug toxicity, lymphomas, eosinophilic granuloma), these diagnostic CT features were always present. In 50/54 cases, a histologic proof was obtained. In 36 patients with histologic confirmation of four different diseases and in six normal controls, we compared sensibility, specificity, and accuracy of chest radiography, chest CT, and HRCT and found the highest diagnostic accuracy by HRCT together with standard CT.